In almost all water distribution systems, the monitoring and maintenance of water quality is an important concern. All water systems, including the ultraclean water systems such as are used in the electronics industry, are prone to the formation of biofilms, which are films that result from the adhesion and subsequent proliferation of bacteria and other life forms on the internal walls and surfaces of such water systems. In almost all instances, such biofilms tend to degrade system performance, and in the case of potable water systems, can potentially result in serious adverse health effects in humans.
For long duration spaceflights and space missions associated with the deployment of space stations or the establishment of lunar and planetary bases, an assurance of potable and hygiene water systems is of a very high priority. For such long duration missions, the capability of recycling used waters to potable quality is a necessity. The ability to recycle water from humidity condensate wash water, or similar related sources, as is planned for long duration space missions, is presently based on generally unproven technology. Since water microbial quality requirements for such space missions are especially stringent, typically requiring a bacterial count of not more than 1 colony-forming unit per 100 ml of water, an ability to monitor the development of biofilms in the various water distribution systems so as to assist in maintenance of water quality has involved extensive research. Heretofore, biofilm monitoring methods and apparatus have almost always been associated with compromises of system sterility which cast doubt upon the validity of data acquired subsequent to extraction of biofilm samples.
Prior methods have included the provision of a tubular spool in the flow line of the distribution system wherein the internal cylindrical surface of the spool provides a sampling surface suitable for the accumulation and growth of biofilms thereon. At an appropriate time interval, the system is temporarily shut down and the spool removed therefrom to permit dissection of its biofilm sample surface into a plurality of samples by sawing, cutting or the like whereby a variety of biofilm analysis procedures may be applied to the individual sample pieces. The resultant heat which is generated in the dissection procedure and the likelihood of sample contamination are deterrents to accurate biofilm evaluation and monitoring procedures which typically involve microbe enumeration, microscopy examinations which may include epifluorescent microscopy and scanning electron microscopy examinations.
A published article entitled "BIOLOGICAL FOULING 0F INDUSTRIAL WATER SYSTEMS A Problem Solving Approach" by Water Micro Associates of San Diego, California, 1987, discloses a "Robbins Biofilm Sampler" designed to provide replicate surfaces for studies of microbial attachment and subsequent biofilm formation. The surfaces are placed at various test locations in the system and after various periods of exposure are recovered from each test site. The potential for system contamination during the removal process is unacceptable for monitoring procedures where it is necessary to maintain a very high water quality. It is also not feasible or convenient to divide the sample surfaces into several portions to support different types of analyses. Further, the Robbins Biofilm Sampler does not provide a duel microbial barrier following coupon extraction.